多孔碳涂覆层对高硫载量电极的改性研究

High Loading Sulfur Electrode Modified by Porous Carbon Layer

锂硫电池具有能量密度高、对环境友好,原材料廉价等优势,有望成为下一代最有发展潜力的动力电池之一。但锂硫电池的库伦效率低、循环性能差是制约了其实用化的主要障碍。通过在高硫载量硫/碳(S/SP(super-P)/CNT(carbon rano tube),硫载量为90%)电极的表面涂覆一层非活性物质层(多孔碳层),制备了带涂覆层的S/SP/CNT复合电极(C-S/SP/CNT复合电极)。采用热重(TGA)方法分析了S/SP/CNT复合材料中硫的含量。采用场发射扫描电子显微镜(FESEM)对复合电极(C-S/SP/CNT)循环前后的表面形貌进行了表征。结果表明, S/SP/CNT复合材料中硫含量高达90%,循环100周后电极的表面没有明显的团聚现象。碳多孔层不但能够物理吸附充放电过程中溶解在电解液中的多硫化物,抑制穿梭效应,且其良好的导电能力,能进一步提高电极的导电性能,增加电极反应的活性位点。采用恒流放电的方法对复合电极的电化学性能进行了测试。C-S/SP/CNT复合电极的首次放电容量达1192.3 mAh·g^(-1),循环300周后的可逆容量仍有442.9 mAh·g^(-1),表现出良好的循环性能。

Lithium-sulfur battery is one of the most promising energy storage system in next-generation electrical vehicles,because of its high energy density with environmental friendliness and low cost.However,the practical application of lithium-sulfur battery is still greatly impeded by the low coulombic efficiency and the poor cycle performance.In this paper,the high-loading sulfur-carbon (S/SP (super-P)/CNT(carbon nano tube),sulfur-loaded 90%) electrode with inactive material layer (porous carbon layer,C-S/SP/CNT electrode) was prepared.The content of sulfur about the S/SP/CNT composites was analyzed by thermogravimetric (TGA) method.The surface morphology of the composite electrode (C-S/SP/CNT) before and after cycling was characterized by field-emission scanning electron microscopy (FE-SEM).The results revealed that the content of sulfur about the S/SP/CNT composite was up to 90%,and there was no obvious agglomeration on the surface of the electrode after 100 weeks.The porous carbon layer could not only physically adsorb the polysulfide which was dissolved in the electrolyte during charge and discharge,and inhibition the shuttle effect,but also the good conductivity could further improve the conductivity of the electrode and increase the active site of the electrode reaction.The electrochemical properties of the composite electrode were analyzed by the methods of galvanostatic discharge.The C-S/SP/CNT composite electrode had an initial specific discharge capacity of 1192.3 mAh·g^-1 and a reversible specific capacity of 442.9 mAh·g^-1 at the 300th cycle,and exhibited a good cycling performance of Li-S batteries.